A smart phone typically employs an architecture composed of an application processor and a communication processor, where the communication processor serves as a peripheral of the application processor and connected thereto via a fixed interface.
Currently, there are generally the following two types of interfaces for connecting the application processor with the communication processor.
Specifically, on one hand, a Universal Asynchronous Receiver/Transmitter (UART) interface can be used to connect the application processor (AP) with the communication processor (CP). A modem interface instruction set (AT command) can be used for communication. Power management can be implemented between the AP and the CP by a handshake protocol. In a sleep state, the power consumption of the UART interface is approximately 5 uA, while in a communication state, the power consumption can be lower than 5 mA due to simplicity of the UART interface protocol. Meanwhile, as the UART interface is an internal connection interface of a chip, its level can be typically set as a digital IO voltage 2.8V or even 1.8V. Thus, the power consumption of the UART interface communication is quite low. That is, for UART, the power consumption can be 5 uA*1.8V=0.01 mW in the sleep state and 5 mA*1.8V=9 mW in a data transmission mode. However, the maximum rate for the UART interface communication is only 3 Mbps, which can only satisfy the requirements of the second generation Mobile network communication systems and fails to satisfy the increasingly high rate of the third or fourth generation Mobile network communication systems.
On the other hand, a USB interface can be used to connect the AP with the CP. The full rate of a USB interface can be up to 12 Mbps, while the high-speed USB, such as USB 2.0, can be up to 480 Mbps, which can satisfy the requirements of the subsequent third generation HSPA or fourth generation mobile communication systems. This can be implemented by multiplexing USB interfaces into a UART interface which uses the AT command for communication between the AP and the CP. Since the maximum rate of the USB interface can be as high as 480 Mbps, the requirements of the subsequent third/fourth generation communications can be fully satisfied. However, the high rate comes at the expense of high power consumption. In addition, the power management between the AP and the CP is conducted using a remote wakeup function of the USB protocol. When there is no data exchange, the USB is suspended and its interface power consumption is higher than 1 mA. When there is data transmission between the AP and the CP, the power consumption of the USB interface is higher than 60 mA. The power consumption of the USB interface is relatively high due to its high voltage. Specifically, the power consumption of the USB interface is 1 mA*3.3V=3.3 mW in a suspended mode and 60 mA*3.3V=200 mW in a data transmission mode.
Although the high-speed USB can satisfy the requirements of the subsequent third or fourth generation mobile communication systems without being a bottleneck of wireless communication, the high power consumption of the USB can be problematic since the AP, serving as the USB host, is always connected to the CP. However, high-speed transmission is not always required during actual communication, where applications are mostly voice calls, video calls and other low-speed data transmissions. Further, as the AP of a mobile terminal serves as a USB HOST during communication with CP, if the AP additionally serves as a USB OTG interface for the mobile terminal, the mobile terminal cannot function as a USB CLIENT device during communication.
In research and practice of the prior art, the following discoveries are made by the inventor. Currently, by using a UART interface to connect the AP with the CP, only the requirements of the second and third generation communications can be satisfied. On the other hand, by using a high-speed USB interface to connect the AP with the CP, the requirements of the third or fourth generation communications can be satisfied. However, the power consumption increases with the increase of the rate and the USB complicated protocol. That is, the tradeoff between the rate and the power consumption cannot be obtained by any interface of prior art which connects the AP with the CP. In other words, the data transmission interfaces cannot be switched adaptively according to the data traffic of the data transmission.